Device responsive to unbalance in polyphase circuit voltages and currents



E. GRASSOT DEVICE RESPONSIVE To UNBALANCE IN POLYPHA'SE CIRCUIT VOLTAGES AND CURRENTS Original Filed Aug. 1S 192 Fig.1.

Ihvenbov: Emile Gr as s ob.

Patented July 28, 1931 UNITED STATES PATENT OFFICE EMILE GRASSOT, OF MEUDON, FRANCE, ASSIGNOR T0 GENERAL ELECTRIC COMPANY,

A CORPORATION OF .NEW YORK DEVICE RESPONSIVE T0 UNBALANCE 11v POLYPHASE CIRCUIT VOLTAGES AND oUnREN'rs Original application filed August 1 3, 1926, Serial No. 129,032, and in France December 23, 1925. Divided and this application filed October 25, 1930. Serial No. 491,232.

My invention relates to improvements in devices responsive to unbalance in polyphase circuit voltages and currents and more particularly relays, metering apparatus, etc, which operate in response to phase sequence components of the power of an electric circuit and an object of my invention is to provide improved and simple apparatus whereby to obtain operation in accordance with a given phase sequence component of the power of an alternating current circuit.

In measuring apparatus, relays and. devices for line protection which take into sccount unbalanced voltages or currents, the

equivalence between a system of any g-vectors which are concurrent and situated in one plane and gsystems each made up of q-symmetrical vectors (systems of balanced vectors) is employed. These vectors represent the components of an electric quantity, such as polyphase alternating voltages, currents, ampere turns, fluxes or magnetic fields, etc, according to the case in point.

- In oneof these systems, called the positive phase sequence system, two cyclically consecutive vectors form between each other an 2w angle in the positive direction. In another system, called the negative phase se- 2 of 17: in a direction opposite to that of the preceding. p

In order'to obtain the positive or negative phase sequence components of the currents, voltages, powers, etc., or of the functions of these quantities, circuit arrangements are generally utilized. The system from which the symmetrical components are thus obtained has the same number of phases the basic or fundamental system. Thus, for example in the case of a system of threephase currents, the positive or negative base sequence components of ampere turns forming part of a three-phase system, etc, can be obtained.

It may be desirable to obtain the positive and negative phase sequence components or balanced to the same extent, c as the three-phase system under consideration, 1)

being the length of one of the vectors of the positive phase sequence system and I the length of a vector of the negative phase sequence system.

In this connection the given system of voltages or currents, takenas three-phase will be converted into a two-phase system of currents, voltages, ampere turns, fields or magnetic fluxes, etc., unbalanced to the same extent, that is the ratio of the positive and negative phase sequence components of each system is the same. Suitable circuit arrangements'will then be applied to this latter equipment enabling itspositive or negative phase sequence components or functions thereof to be obtained or circuit arrangements will be used starting from a threephase system of voltages or currents onabling the positive or negative phase sequence components or functions thereof to be obtained directly from a two-phase system unbalanced to the same degree as the first.

My invention includes line protecting devices, relays, measuring apparatus and devices in which the unbalance of the circuits or lines, characterized by the application of the principles indicated above, that is, by

the use of devices some of which are known to the art such as the Scott system, rotating field phase, transformers,etc., plays a part enabling the positive or negative phase sequence components or functions thereof of a system with a number of phases differing from that of the circuit to be protected or on which the measurements are taken, to be obtained.

The number of phases of the intermediary system will bcchosen so as to simplify the construction of the apparatus or other circuit arrangements. Further, the passing from one system to another may be made outside or inside the apparatus or device.

My invention will be better understood from the following description when considered in connection with the accoziqnlnying drawings and its scope will be pointed out in the appended claims.

This application is a division of my application, Serial No. 129,032, filed August 13,

1W3, for devices responsive to unbalanced cu 'ents or voltages.

In the accompanying drawings Fig. 1 illustrates diagrammatically electroresponsive apparatus embodying my invention; Fig. 2 illustrates diagrammatically a modification of my invention and Figs. 3 and et are vector g'ams explanatory of my invention.

In the illustrated embodiments of my invention, it will be assumed that power measurements are to be made on a threephase system or that a three-phase circuit is to be protected and that the three-phase system of voltages or currents may be transformed into a two-phase system ot voltages, :miperc-turns, fluxes, magnetic fields. etc., or that the positive or negative phase sequence components of these values or of the active. reactive or complex power in the latter system are obtained. This transformation enables the essential properties of twophas stems to be utilized, that is to have only two vectors which in balanced systems are. 90 out of phase with each other.

In Fig. 3, let X and X be the two vectors of a two-phase system. The positive phase sequence component of the vector X will be \Yllvle .'l /-1, and the negative phase sequence component will be From these formulae, twice the postivc I Y r phase sequence components 2\, and 233 are obtained by adding to X, a vector jll v 1r equal to A: and leading 3 in. order to ob tain 2X and by adding to X a vector 7T fie; equal to X and lagging 5 in order s OY to obtain M In order to obtain the negative phase sequence components, vectors are added to X, and K, respectively equal to and directly opposite to those used for the positive phase sequence components.

23 311' i 11' a and a respectively 1n a suitable direction. Similarly, in order to obtain the positive and negative phase sequence components of X a vector oi length X added geometrically to X making with r 371' L angles ol- -11 and a; respectively in a suitable direction.

Often the length of X or X- only is required or of X or X In this case, to obtain for example the positive phase quence component, a vector X, may be taken instead oi X, of length A-X, equal to or proportional to the length of X, and out of phase with respect to it by an angle [3 lagging for example as shown in Fig. 4;. If a vector X: is added to it of length X. equal or proportional to X with the same cocilicient of proportion, but l ading' by 71' (W) with respect to X the resultant of the two vectors thus obtained will give a vector X of length llX equal or proportional to X and lagging it by angle ,5. Similar remarks can be made concerning the other components of X and i From the foregoing, it follows that values can be obtained equal or proportional to the positive or negative phase sez' ucnce components of the given out-ot-phase values by Inoducing suitable phase displacements, leading or lagging, of angles (littering from 71' 5 with respect to X hence by 7T 5 by means of resistances, reactances, sell or mutual. inductances, capacities, transformers, sl1ortcircuited windings, etc.

For operation in response to a given phase sequence component of power, one of the systems of values, for example the voltages. can be transformed into twophase and the other, for example the currents, left in liree-phase form, or the voltages and currents can be transformed from three-phase to twophase and the two negative (or positive) phase sequence components of the voltages can be acted upon by the two-phase currents themselves or vice-versa. It can be shown that, in these cases, torques are obtained depending on only the positive or negative phase sequence component of the power, that is a symmetrical phase sequence component oi the power.

Fig. 1 shows the wiring diagram of an sis induction disk type of relay or wattmeter measuring the negative (or positive) phase sequence components of power; a and a are two voltage windings; I), b the current windings on the corresponding electromagnets; D a disk; S a Scott transformer; T T T three current transformers which feed b with current proportional to the current 2' of phase 3 and the coil 6 with current proportional to (i 'i the difference between the currents i and 2' of phases 1 and 2; and 1', 1", 13, W r r' 8,, 8' 8 8' 8, s are resistances and reactances which produce the necessary phase displacements in order to obtain the negative (or positive) phase sequence components of two-phase voltages given by the secondaries 1 and 2 of the Scott system.

In this case there is combined with a system of three-phase currents changed to a system of two-phase currents unbalanced to the same degree, a system of three-phase voltages changed to a system of two-phase voltages whose desired phase sequence component is segregated by means of the circuit arrangement embodying the resistances r and reactances s. Inasmuch as the currents in the windings a, a are proportional to the negative (or positive) phase sequence components of the voltages, the relay is influenced solely by the negative (or positive) phase sequence components of the power for only the fluxes due to the negative (or positive) phase sequence components of the currents in the windings b, I) combine with the fluxes due to the voltages on the windings a, a to produce a torque on the disk D.

Fig. 2 is a wiring diagram for a wattmeter or wattmetric relay for measuring the negative phase sequence component of power in which two negative phase sequence components of ampere-turns are obtained 90 out of phase with each other, that is to say the two negative phase sequence components of a two-phase system of values proportional to the negative phase sequence components of the given three-phase voltage system, Without transforming the threephase voltage system into a two-phase system unbalanced to the same degree.

In this figure 1, 2, 3 represent the three line wires of a three-phase circuit through which the currents 2' 2' 2' flow; a, a a double voltage winding of an electromagnet,

' of which 6 is the current coil a, a I) are the respective windings of a second electromagnet; 1', 1 7* are resistances; s, 8 8 are reactances, allowing resultant ampere-turns to be produced in a, a proportional to the negative phase sequence component of the voltage 15. and 1n a, (1' a component equal to the preceding one and out of phase with respect to 1t. In practice the current in a can be in phase with u that in an, 60 lagging on a the current in a" will lag 10 and that in a, will lead a 30. T T T represent three current transformers enabling ampere-turns in quadrature to be obtained in the current coils b and Z). r

In this case there is combined with a system of three-phase currents changed to a system of two-phase currents unbalanced to the same degree asystem of three-phase voltages whose negative phase sequence component is segregated by means of the circuit arrangement embodying the resistances r and reactances a. It will be noted that with both of the illustrated embodiments of my invention it is-necessary to segregate the phase sequence components of only one of the factors, current and voltage, which go to makeup the power. For the sake of convenience, simplicity and accuracy it is better to use the segregating networks or circuits with the voltage and with the current, although my invention is not so limited but, in accordance with my invention, it is suflicient to segregate the phase sequence component of only one of the quantities, either the current or the voltage.

The desired phase displacements can be effected by windings short-circuited through variable resistances, said windings being associated with the voltage and current circuits and thereby affording means of acting on the phase displacements of the negative phase sequence components of the fluxes ofthe voltage circuits or on the fluxes of the current circuits. The currents could also be combined in a manner differing fromv that indicated in the figures, without dcparting from the scope of my invention.

While I have shown and described by invention in considerable detail, I do not desire to be limited to the exact arrangements shown, but seek to cover in the appended claims all those modifications that fall within thetrue spirit and scope of my invention.

WVhat I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination with a three-phase circuit, a relay having two current windings respectively connected to be energized in accordance with the current in one phase conductor and the difference between the currents in the remaining two phase conductors and voltage windings arranged to cooperate with said current windings and connected to be energized in accordance with the negative phase sequence components of the voltages of a two-phase system having efiective values dependent on the components of the voltages of the three-phase circuit.

2. In combination with a three-phase circuit, a relay having two current windings respectively connected to be energized in accordance with the current in one phase III) conductor and the difference between the cur rents in the remaining two phase conductors and voltage windings arranged to cooperate with said current windings and connected to e energized in accordance with one of the -vynnnetrical phase sequence components of the voltages of the circuit.

3. In combination with a three-phase electric circuit, a wattmetric device responsive to a symmetrical phase sequence component of e power of the circuit including cooperating current and voltage means, said current means being connected to said circuit to be energized in accordance with a twophase system of currents unbalanced to the same extent as the currents of the threephase circuit and means for energizing said voltage means in accordance with one of the symmetrical phase sequence components of a two-phase system of voltages unbalanced to the same extent as the voltages of the three-phase circuit.

i. In combination with a polyphase circircuit, a wattmetric device responsive to a symmetrical phase sequence component of the power of the circuit including cooperating current and voltage winding means, said current winding means being connected to be energized by more than one of the phase sequence components of the currents in the phase conductors oi the circuit and means for energizing the voltage winding means in accordance with only one of the symmetrical phase sequence components of the voltages of the circuit.

In combination with a threephase circuit, a wattmetric device responsive to a symmetrical phase sequence component of the power of the circuit including cooperating current and voltage means, said current means being connected to said circuit to be energized in accordance with a twophase system of currents unbalanced to the same extent as the currents of the threephase circuit and means for energizing said v ltage means in accordance with one of the symmetrical phase sequence components of the voltages of the three-phase circuit.

6. In combination with a polyphase circuit, a wattmetric device responsive to a symmetrical phase sequence component of the power of the circuit including cooperating means for producing an efi'ect dependent on the product of two quantities, the current and the voltage, of the circuit, one of said means being connected to be energized by more than one of the phase sequence components of the power of one of said quantities and means for energizing the other of said cooperating means only in accordance with a symmetrical phase sequence coiponent of the other of said quantities.

7. In combination with a polyphase circuit, an induction disk device responsive to the negative phase sequence component of Certificate of Correction Patent No. 1,816,729. Granted July 28, 1931, to EMILE GRASSOT It is hereby certified that error appears in the printed specification of the abovenumbered patent requiring correction as follows: Page 2, lines 45 to 47, strike out the formula and insert instead I 2X2 =X2 ].X1= 2jX1 page 3, line 105, for by read my; and that the said Letters Patent should be read With these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 15th day of September, A. D. 1931.

[emu] M. J. MOORE,

Acting Commissioner of Patents.

Certificate of Correction Patent No. 1,816,729. Granted July 28, 1931, to EMILE GRASSOT It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, lines 45 to 17, strike out the formula and insert instead I 2X2 =X2 jX1 'I 2jX page 3, line 105, for by read my; and that the said Letters Patent should be read With these corrections therein that the same may conform to the record of the case in the Patent Oflice. Signed and sealed this 15th day of September, A. D. 1931.

[smn] M. J. MOORE,

Acting Commissioner of Patents. 

